As part of the Sarah Project, building the tight squish B230FT engine required a good cylinder head.

And part of the cylinder head program involves camshaft choice. The debate rages --amongst the fans of the turbo'd "Bricks"-- as to what the "best" cam is for a redblock turbo. Few can agree on any particular camshaft offered by Volvo or the aftermarket. It really does end up as a trial and error procedure to find the 'best' one...

...because personal preference, based on desired power curve and other criteria, becomes the subjective determiner.

[...and yes, I have my own opinions and preferences, based on my goals and objectives for a particular build.]

Discounting the 'subjective' side of the choice, the largest problem affecting making a cam choice has been the difficulty in determining what the actual specifications of the factory camshafts are. The factory specifications given in factory publications were not, and are not precisely comprehensible; nor are those specifications easily translatable into data for comparative purposes.

[That problem is being addressed by some enthusiasts who seek to push back the darkness. I became aware of this independent effort to accurately quantify camshaft specifications via actual measurement after I had already performed my dimensioning tests of the T and A camshafts. My results are different primarily because I chose to use 0.020in valve lift as my reference point.]

I needed to know some things about the camshaft that was in the engine; and what the possibilities were for an upgrade in the future. But one does not make changes based on ignorance: if you do not know what you have; then how can you know if something else is better? Comparisons have to be based on certain common grounds in order to be valid.

Because of the discrepancies in specifications listed for the factory cams that I have read online and elsewhere; and because of apparent contradictions I thought that I saw in those listings: both amongst themselves, and even in published factory service manuals; I decided to check it out for myownself. I could not afford to guess. Not knowing for sure was no longer an option.

Ignorance is NOT bliss.

The first step was to actually take physical measurements of the camshafts in question; in a consistent, repeatable, and verifiable procedure. Once the actual differences were quantified, I could then use that information to evaluate those camshafts. The camshafts I wanted to measure and compare first are the two camshafts that Volvo used in turbo motors in the various markets: the T and the A camshafts.

Going through this discovery program brought home another rule of thumb: Knowing something and realizing it's value are often two different things. I have known for years how the valvetrain works. But it wasn't until I actually measured what was going on and when it was happening that I was able to see the genius of the design.

The Volvo SOHC camshaft design is a direct-acting flat tappet design. It does not use rocker arms to affect the opening and closing of the valves. Rocker arms are used to mulitply the total lift of the cam lobe; usually at about a 1.5:1 ratio. This is a lift amount multiplier effect. A secondary effect of the rocker arm ratio is to increase the rate of valve opening and closing: this is the lift rate multiplier effect.

The Volvo design incorporates the mushroom lifter effect to increase valve opening speed [the lift rate multiplier]. While different from what a rocker arm does [multiplying lobe lift at the valve, primarily, and speeding up valve open/close speeds secondarily]; the mushroom lifter effect does speed up the opening and closing speeds of the valve. The total valve opening distance is still 1:1 with the mushroom effect [whatever the max lift of the lobe is; that is the max lift at the valve]. But using the mushroom effect gets the valves open faster and closed faster.

The Volvo SOHC valvetrain has a minimum number of moving parts. The incorporation of the mushroom effect enhances valve opening and closing; speeding up the opening and closing of the valves smoothly and reliably. Without the added weight, complications and wear factors associated with pushrods, rocker arms, and or sliders, the Volvo valvetrain does not require high valve spring pressures to control all that superfluous mass.

To borrow and twist a phrase: 'rocker arms? we don't need no stinkin' rocker arms!'

View and read on...maybe you will see the beauty of the design as well.


--I hope to do some further investigations of some other volvo cams as time permits. I want to look at the factory B, D, and V grinds. The V definitely has my interest piqued. And, there are some very interesting aftermarket camshafts available as well. A prime example of that is the KG2T from KG Trimning.--